This invention relates to improvements in an apparatus for applying the control signals of an elevator as inputs.
In an elevator, a large number of control signals are exchanged between a machinery room and a car. A signal inputting apparatus is as shown in FIG. 1.
Referring to the figure, numeral 1 designates a power supply bus. External signal elements, such as relay contacts or switches, 21-2n are connected to the power supply bus and generate the control signals of the elevator. Signal inputting circuits 31-3n are respectively connected to the external signal elements 21-2n and comprise respective protective resistors 41-4n and photocouplers (each consisting of a light emitting diode and a phototransistor) 51-5n. Terminals 61-6n are respectively connected to the output sides of the signal inputting circuits 31-3n and transmit signals to an elevator control device (not shown).
For example, when the external signal element 21 is open, the photocoupler 51 does not turn "on", and a voltage at a level which is determined by the voltage of the power supply bus 1 appears at the terminal 61. On the other hand, when the external signal element 21 is closed, the photocoupler 51 turns "on", and the voltage of the terminal 61 becomes null. Thus, the signal is transmitted to the elevator control device.
In this case, supposing that the external signal elements 21-2n are installed in the car and that the remaining parts are installed in the machinery room, wiring leads connecting the power supply bus 1 and the external signal elements 21-2n must be provided as wires in a moving cable between the machinery room and the car. Therefore, as the number of the external signal elements 21-2n increases, the number of the wires in the moving cable also increases to render the apparatus expensive. Other problems are that, the increase in the number of the wires in the moving cable also complicates the installation work thereof, and also increases the weight of the moving cable which requires an increased capacity of a hoist.
Moreover, when a part of the circuitry is shorted, a fuse (not shown) connected to the power supply bus 1 blows out. The fuse must be replaced each time, which is troublesome.